p-throttle

Throttle promise-returning & async functions

It also works with normal functions.

Useful for rate limiting calls to an external API, for example.

Install

$ npm install p-throttle

Usage

Here, the throttled function is only called twice a second:

const pThrottle = require('p-throttle');

const now = Date.now();

const throttle = pThrottle({
	limit: 2,
	interval: 1000
});

const throttled = throttle(index => {
	const secDiff = ((Date.now() - now) / 1000).toFixed();
	return Promise.resolve(`${index}: ${secDiff}s`);
});

for (let i = 1; i <= 6; i++) {
	throttled(i).then(console.log);
}
//=> 1: 0s
//=> 2: 0s
//=> 3: 1s
//=> 4: 1s
//=> 5: 2s
//=> 6: 2s

API

pThrottle(options)

Returns a throttle function.

Returns a throttled version of fn.

options

Type: object

Both the limit and interval options must be specified.

limit

Type: number

Maximum number of calls within an interval.

interval

Type: number

Timespan for limit in milliseconds.

strict

Type: boolean
Default: false

Use a strict, more resource intensive, throttling algorithm. The default algorithm uses a windowed approach that will work correctly in most cases, limiting the total number of calls at the specified limit per interval window. The strict algorithm throttles each call individually, ensuring the limit is not exceeded for any interval.

throttle(function_)

function_

Type: Function

Promise-returning/async function or a normal function.

throttledFn.abort()

Abort pending executions. All unresolved promises are rejected with a pThrottle.AbortError error.

throttledFn.isEnabled

Type: boolean
Default: true

Whether future function calls should be throttled and count towards throttling thresholds.

Related

• p-debounce - Debounce promise-returning & async functions
• p-limit - Run multiple promise-returning & async functions with limited concurrency
• p-memoize - Memoize promise-returning & async functions
• More…